The present invention relates to integrated logic circuits and, more particularly, to a circuit and method for providing electrical identification of different families of such circuits having identical functionality but different input/output behavior without the need for requiring extensive testing at the manufacturing process level.
Semiconductor manufacturers of standard logic integrated circuits often provide two or more families or versions of circuits having the same logic functions but different input/output characteristics. An example of the foregoing are the 10E and 100E Emitter-Coupled-Logic (ECL) families manufactured by Motorola, Inc. The 10E and 100E family of products provide the same logic functions but have different biasing requirements and output characteristics with temperature. Moreover, each particular logic circuit of each family is produced from the same mask set such that it is impossible to tell which family to which the logic circuit belongs without testing.
Since the functionality of the two families of logic circuits are the same it is necessary to provide some means at the manufacturing and test level to identify to which a family the ECL circuit belongs. This is needed to prevent substitution of an ECL circuit from one family with that of another logic family by mistake.